Clarify additional provider archive input

docs/provider-icon-import.md

@@ -28,11 +28,11 @@ stack icons import aws ~/Downloads/aws-icons.zip \
 
 The manifest follows the public [`stack-sh/theme` provider-pack schema](https://github.com/stack-sh/theme/blob/main/PROVIDER_PACKS.md). It records the official source, archive and asset hashes, upstream paths, allowed output categories, transformations, official product names, terms URL, review date, and non-endorsement notice.
 
-Google publishes the audited core-product and category icons as separate archives. Supply both local files explicitly:
+Google publishes the audited core-product and category icons as separate archives. The positional `ARCHIVE` is the primary core-products ZIP. `--source categories=<ARCHIVE>` maps the second local ZIP to the required `categories` source ID; it is not a URL and does not download anything.
 
 ```sh
-stack icons import gcp ~/Downloads/core-products-icons.zip \
-  --source categories=~/Downloads/category-icons.zip \
+stack icons import gcp /path/to/core-products-icons.zip \
+  --source categories=/path/to/category-icons.zip \
   --accept-terms \
   -o .stack-icons/gcp
 ```

src/lib.rs

@@ -31,7 +31,7 @@ const FORMAT_HELP: &str = "Format Stack source canonically\n\nUsage:\n  stack fm
 const RENDER_HELP: &str = "Render Stack source as standalone SVG\n\nUsage:\n  stack render <FILE> [--provider-pack <DIRECTORY>]... [-o <OUTPUT>] [--notice <NOTICE>]\n\nArguments:\n  <FILE>                     Read Stack source bytes from this file\n\nOptions:\n  --provider-pack <DIRECTORY> Load one local imported provider pack; repeatable\n  -o <OUTPUT>                 Write SVG atomically instead of using standard output\n  --notice <NOTICE>           Write exact used-provider notices atomically\n";
 const ICONS_HELP: &str = "Manage local provider icon packs\n\nUsage:\n  stack icons list [PROVIDER] [QUERY]\n  stack icons import <PROVIDER> <ARCHIVE> [--source <ID>=<ARCHIVE>]... --accept-terms -o <DIRECTORY>\n\nProviders:\n  aws            305 AWS Architecture Icons\n  gcp             45 Google Cloud product and category icons\n  azure          639 Azure Public Service Icons\n  simple-icons    62 curated developer and collaboration tools\n";
 const ICONS_LIST_HELP: &str = "List searchable asset-free provider catalog metadata\n\nUsage:\n  stack icons list\n  stack icons list <PROVIDER> [QUERY]\n\nArguments:\n  <PROVIDER>  aws, gcp, azure, or simple-icons\n  [QUERY]     Case-insensitive ID, product, or category substring\n";
-const ICONS_IMPORT_HELP: &str = "Import audited provider icon archives locally\n\nUsage:\n  stack icons import <PROVIDER> <ARCHIVE> [--source <ID>=<ARCHIVE>]... --accept-terms -o <DIRECTORY>\n\nArguments:\n  <PROVIDER>   aws, gcp, azure, or simple-icons\n  <ARCHIVE>    Local primary ZIP archive; Stack performs no download or upload\n\nOptions:\n  --source <ID>=<ARCHIVE>  Supply a required additional local archive; repeatable\n  --accept-terms           Confirm that you reviewed all provider and brand terms\n  -o <DIRECTORY>          Create a new local pack directory atomically\n";
+const ICONS_IMPORT_HELP: &str = "Import audited provider icon archives locally\n\nUsage:\n  stack icons import <PROVIDER> <ARCHIVE> [--source <ID>=<ARCHIVE>]... --accept-terms -o <DIRECTORY>\n\nArguments:\n  <PROVIDER>   aws, gcp, azure, or simple-icons\n  <ARCHIVE>    Local primary ZIP archive; Stack performs no download or upload\n\nOptions:\n  --source <ID>=<ARCHIVE>  Map an additional local ZIP by source ID; GCP requires categories=<PATH>\n  --accept-terms           Confirm that you reviewed all provider and brand terms\n  -o <DIRECTORY>          Create a new local pack directory atomically\n";
 const MAX_PROVIDER_MANIFEST_BYTES: usize = 1024 * 1024;
 const MAX_PROVIDER_ASSET_BYTES: usize = 1024 * 1024;
 const MAX_PROVIDER_PACKS: usize = 32;